﻿// Copyright (C) 2016 Keijiro Takahashi
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//

//
// This script is based on the original implementation by Ken Perlin
// http://mrl.nyu.edu/~perlin/noise/
//

using UnityEngine;

namespace Slate
{

    public static class Perlin
    {

        public const float FBM_NORM = 1 / 0.75f;

        public static float Noise(float x) {
            var X = Mathf.FloorToInt(x) & 0xff;
            x -= Mathf.Floor(x);
            var u = Fade(x);
            return Lerp(u, Grad(perm[X], x), Grad(perm[X + 1], x - 1)) * 2;
        }

        public static float Noise(Vector2 coord) { return Noise(coord.x, coord.y); }
        public static float Noise(float x, float y) {
            var X = Mathf.FloorToInt(x) & 0xff;
            var Y = Mathf.FloorToInt(y) & 0xff;
            x -= Mathf.Floor(x);
            y -= Mathf.Floor(y);
            var u = Fade(x);
            var v = Fade(y);
            var A = ( perm[X] + Y ) & 0xff;
            var B = ( perm[X + 1] + Y ) & 0xff;
            return Lerp(v, Lerp(u, Grad(perm[A], x, y), Grad(perm[B], x - 1, y)),
                           Lerp(u, Grad(perm[A + 1], x, y - 1), Grad(perm[B + 1], x - 1, y - 1)));
        }


        public static float Noise(Vector3 coord) { return Noise(coord.x, coord.y, coord.z); }
        public static float Noise(float x, float y, float z) {
            var X = Mathf.FloorToInt(x) & 0xff;
            var Y = Mathf.FloorToInt(y) & 0xff;
            var Z = Mathf.FloorToInt(z) & 0xff;
            x -= Mathf.Floor(x);
            y -= Mathf.Floor(y);
            z -= Mathf.Floor(z);
            var u = Fade(x);
            var v = Fade(y);
            var w = Fade(z);
            var A = ( perm[X] + Y ) & 0xff;
            var B = ( perm[X + 1] + Y ) & 0xff;
            var AA = ( perm[A] + Z ) & 0xff;
            var BA = ( perm[B] + Z ) & 0xff;
            var AB = ( perm[A + 1] + Z ) & 0xff;
            var BB = ( perm[B + 1] + Z ) & 0xff;
            return Lerp(w, Lerp(v, Lerp(u, Grad(perm[AA], x, y, z), Grad(perm[BA], x - 1, y, z)),
                                   Lerp(u, Grad(perm[AB], x, y - 1, z), Grad(perm[BB], x - 1, y - 1, z))),
                           Lerp(v, Lerp(u, Grad(perm[AA + 1], x, y, z - 1), Grad(perm[BA + 1], x - 1, y, z - 1)),
                                   Lerp(u, Grad(perm[AB + 1], x, y - 1, z - 1), Grad(perm[BB + 1], x - 1, y - 1, z - 1))));
        }




        public static float Fbm(float x, int octave) {
            var f = 0.0f;
            var w = 0.5f;
            for ( var i = 0; i < octave; i++ ) {
                f += w * Noise(x);
                x *= 2.0f;
                w *= 0.5f;
            }
            return f;
        }

        public static float Fbm(float x, float y, int octave) { return Fbm(new Vector2(x, y), octave); }
        public static float Fbm(Vector2 coord, int octave) {
            var f = 0.0f;
            var w = 0.5f;
            for ( var i = 0; i < octave; i++ ) {
                f += w * Noise(coord);
                coord *= 2.0f;
                w *= 0.5f;
            }
            return f;
        }


        public static float Fbm(float x, float y, float z, int octave) { return Fbm(new Vector3(x, y, z), octave); }
        public static float Fbm(Vector3 coord, int octave) {
            var f = 0.0f;
            var w = 0.5f;
            for ( var i = 0; i < octave; i++ ) {
                f += w * Noise(coord);
                coord *= 2.0f;
                w *= 0.5f;
            }
            return f;
        }




        static float Fade(float t) {
            return t * t * t * ( t * ( t * 6 - 15 ) + 10 );
        }

        static float Lerp(float t, float a, float b) {
            return a + t * ( b - a );
        }

        static float Grad(int hash, float x) {
            return ( hash & 1 ) == 0 ? x : -x;
        }

        static float Grad(int hash, float x, float y) {
            return ( ( hash & 1 ) == 0 ? x : -x ) + ( ( hash & 2 ) == 0 ? y : -y );
        }

        static float Grad(int hash, float x, float y, float z) {
            var h = hash & 15;
            var u = h < 8 ? x : y;
            var v = h < 4 ? y : ( h == 12 || h == 14 ? x : z );
            return ( ( h & 1 ) == 0 ? u : -u ) + ( ( h & 2 ) == 0 ? v : -v );
        }

        static int[] perm = {
            151,160,137,91,90,15,
            131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,
            190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,
            88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,
            77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,
            102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,
            135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123,
            5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
            223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9,
            129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228,
            251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107,
            49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,
            138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180,
            151
        };
    }
}
